xsession: target i3.service and adapt dependencies

I think this is cleaner to make i3 the pivot. Also, don't make i3
restart i3-session each time it starts.

dotfiles/systemd/i3.service

@@ -2,6 +2,7 @@
 Description=i3 window manager
 PartOf=graphical-session.target
 After=xsession.target
+Wants=xsession.target
 
 [Service]
 ExecStart=/usr/bin/i3

dotfiles/systemd/xsession.target

@@ -4,7 +4,6 @@ BindsTo=graphical-session.target
 Wants=autorandr.service
 Wants=dunst.socket
 Wants=easyeffects.service
-Wants=i3.service
 Wants=inputplug.service
 Wants=picom.service
 Wants=policykit-agent.service

dotfiles/xsession

@@ -38,4 +38,4 @@ dconf load / < ~/.config/i3/dotfiles/dconf.ini
 # Services are started with systemd
 systemctl --user import-environment
 systemctl --user daemon-reload
-exec systemctl --user start --wait xsession.target
+exec systemctl --user start --wait i3.service